The invention relates to a roller screen including a gauze screen, a roll-up mechanism for said gauze screen, a pull beam connected to the free end of said gauze screen, guides for guiding said pull beam and the side edges of said gauze screen, as well as spring hooks cooperating with cams present on the ends of said pull beam, which are mounted in the ends of said guides remote from said roll-up mechanism by a base which fits in the end of the guide. The hooks extend substantially in the longitudinal direction of said guides, and the spring force of said hooks can be adjusted by an adjusting screw mounted in said base.
A roller screen of this kind is known from European patent 579,335. The roll-up mechanism of such a prior art roller screen generally includes a spring, so that the pulled-out gauze screen is tensioned and the gauze screen will constantly tend to roll up again. Since the pull beam is retained in the pulled-out position as a result of the cooperation between the spring hooks and the cams, the gauze screen will be drawn tightly and free of folds before the door or window opening at all times.
With this prior art roller screen, the adjusting screw extends through the base substantially in the longitudinal direction of the guides, and thus substantially parallel to the respective spring hook, and makes contact with a part of the spring hook that extends at an angle to said longitudinal direction. Access to said adjusting screw can be gained only from the side of the base which is present at said end of the guides. The adjustability of the spring force makes it possible to adjust the retaining force between the cams and the spring hooks.
Although this prior art roller screen has proved to be satisfactory in practice, a number of aspects thereof can be further improved. Thus it is not possible in many cases to simply adjust the spring force by manipulating the adjusting screw once the roller screen is mounted in position, because said side of the base is not accessible at the end of the guide. The spring force, once adjusted before the roller screen is mounted in position, can only be changed when the roller screen is at least partially dismounted.
Another disadvantage of the prior art roller screen is the fact that, due to the selected position of the adjusting screw in the longitudinal direction of the guides and the spring hook, the point of application of the adjusting screw on the spring hook varies upon adjustment of the adjusting screw. As a result of this, there is no linear relationship between the movement of the adjusting screw and the increase or decrease of the spring force.
Finally, in some cases, there is a risk that the shifting of the point of application of the adjusting screw will produce a notch effect in the spring hook, due to the sharp screw thread thereof, which will cause damage to the hook and which, in an extreme case, may result in the unintentional collapse thereof.